The present invention relates generally to exhaust nozzle structures for engines providing thrust by expulsion of gaseous products of combustion of fuel, and more particularly to a thrust vectoring nozzle structure incorporating small airfoils in the divergent portion of the nozzle exhaust duct for vectoring thrust.
In thrust-producing engines, such as ramjets, rockets and turbojets, the propulsive nozzle cooperates with the combustor of the engine to convert thermal energy of the gaseous combustion products of fuel burned in the combustor to directed kinetic energy (thrust) at the nozzle exit by the expansion of the gases upon discharge.
Thrust vector control in propulsion nozzles for controlling thrust direction is attained in conventional nozzle structures by various means such as aerodynamic fins, ancillary jets, jet vanes, gimbals and secondary fluid injection. In a converging-diverging overexpanded nozzle, secondary fluid injection has been used for vectoring the primary flow. Typically, secondary fluid is introduced in the diverging portion of the nozzle to cause flow separation and uneven pressure distribution in the nozzle resulting in a laterally directed force.
Confined jet thrust vector control nozzles have a reconverging region downstream of the diverging region. The flow leaves the reconverging region through an exit orifice. This configuration allows for large thrust vector angles of about 20.degree.-30.degree.. Supersonic flow at the exit tends to isolate the flow inside the nozzle from ambient conditions.
The invention herein is an exhaust nozzle structure incorporating small airfoils at the walls defining the divergent portion of an axisymmetric converging-diverging reconverging supersonic nozzle to vector the thrust. Vectoring capability to about 30.degree. is attainable with a small loss in total thrust coefficient. In systems where light weight and large steering vector angles are desirable at the expense of thrust coefficient, the invention avoids the tankage and fluid control systems characteristic of confined jet thrust vector control nozzles, and does not have the inherent altitude limitations of, and can produce much greater vector angles than, boundary layer thrust vector control nozzles.
It is therefore a principal object of the invention to provide an improved exhaust nozzle structure for an engine providing propulsive thrust to a vehicle by expulsion of gaseous products of fuel combustion.
It is a further object of the invention to provide a thrust vectoring exhaust nozzle structure.
It is a further object of the invention to provide a thrust vectoring exhaust nozzle structure utilizing small airfoils in the divergent region of the nozzle.
It is yet a further object of the invention to provide a thrust vectoring exhaust nozzle structure for missile steering control.
These and other objects of the invention will become apparent as a detailed description of representative embodiments proceeds.